Question

You cannot tell________looking at someone whether or not he has HIV.

A．without　B．by

C．for　D．with

 

Answer 1

B

【解析】考查介词辨析。句意：你不可能凭外表来判断一个人是否携带HIV病毒。by意为“通过，用……，靠……”，符合句意。